1. Field of the Invention
The present invention relates to a semiconductor device provided with a light transmissive cover.
2. Description of Prior Art
In a digital mirror device that utilizes a device having, on a silicon substrate, a plurality of micro-mirrors, capable of being driven mechanically, and an electronic circuit, for controlling the motion of the micro-mirrors and that projects an image by digitally controlling the motion of the micro-mirrors so as to reflect light from a light source, a light transmissive cover is attached to the device.
As shown in FIG. 5, a conventional digital mirror device 100 provided with a light transmissive cover is manufactured by positioning a separately fabricated light transmissive cover 106 to cover a device 104 mounted on a mounting substrate 102. The cover is composed of a case 110 formed of metallic material such as kovar (Fe—Ni—Co alloy with coefficient of thermal expansion similar to that of a glass material) and a glass sheet 112 fitted thereinto, and is provided inside with a light interrupting film 114 of CrO2.
Such a cover is fabricated as follows. As shown in FIG. 6(a), a metal material such as kovar is mechanically processed, such as by machining, to form a case 110 having an opening 111. Then, as shown in FIG. 6(b), a glass material 112 is fitted into the opening 111 of the case 110. Subsequently, as shown in FIG. 6(c), the glass material 112 is ground to a thickness corresponding to that of the case. Then, after a CrO2 film is formed on the inside of the case 110 by a process such as sputtering or evaporation, patterning is performed to form a light interrupting film 114, as shown in FIG. 6(d). The cover 106 thus fabricated is subsequently joined to a substrate having a device mounted thereon so as to cover the device to complete a device 100 provided with a light transmissive cover as shown in FIG. 5.
In the conventional device 100 provided with the light transmissive cover manufactured as described above, it was necessary that each case 110, for fixing the light transmissive glass member 112, and each cover glass 112, was processed separately. Therefore, the manufacture required not only much time and labor but also large cost. In addition, as the case 110 was fabricated by machining process, the cover became very large relative to the device 104 when it was assembled into a light transmissive cover 106. It was also disadvantageous that the product precision (quality) was not uniform.
As a prior art, for manufacturing a device provided with a cover, a method is described in JP 2002-43463 A in which a first semiconductor substrate having a semiconductor element formed thereon is joined to a second substrate (a lid substrate) comprising a glass or ceramic cover. In this case, the cover is fabricated by filling the recessed portion of the second substrate for cover with powder material such as glass or the like so as to become flat, and then also making the opposite side of the second substrate flat.
A method is described in JP 2002-246489 A in which, as a wafer level hermetic sealing method, a wafer having a semiconductor element formed thereon and a lid substrate having a lid for cover collectively formed thereon are separately fabricated, and a junction part consisting of solder is formed on the wafer or the lid wafer, and after the two wafers are joined by the junction part, the wafer is diced into chips.